1. Field of the Invention
The present invention relates to a lifting apparatus capable of conveying persons and/or goods from or to different levels by raising a platform from a vehicle and, more particularly, to a lifting apparatus capable of raising a platform to a level and horizontally moving the platform on the level stored in a memory or repeatedly raising the platform to the level stored in the memory.
2. Description of the Prior Art
Lifting apparatus capable of conveying persons and goods from or to different levels by raising or lowering a platform are used widely for assembling work, painting work or repairing work at a high level on expressways and building construction sites. The typical conventional lifting apparatus employs an telescopic pantograph mechanism, namely, a so-called scissors type linkwork, comprising a plurality of pairs of arms each having pair of arms pivotally joined at the middle. In order to increase the maximum lift of such a lifting apparatus, it is necessary to increase the length of the arms or to increase the number of the pairs of arms. Accordingly, such a lifting apparatus having a large lift needs a pantograph mechanism consisting of many links. Therefore, the lifting platform of the lifting apparatus is located at a high level even when the pantograph mechanism is collapsed, and hence it is difficult for persons to get on and off the platfrom and it is troublesome to load and unload the platform.
Lifting apparatus having a single stretchable arm comprising a plurality of telescopically combined booms have been proposed in Japanese Patent Application Nos. 56-134487 and 56-191065.
All those newly proposed lifting apparatus, however, inevitably need an increased number of booms, and hence so many components are necessary, troublesome manufacturing and assembling work is required and the lifting apparatus are expensive. Furthermore, those lifting appatus have so many sliding parts for assembling the booms and arms. Since those sliding parts are provided with sliding members, such as MC nylon members, so many parts need to be replaced periodically requiring large inspection and maintenance costs and troublesome work.
Another lifting apparatus has been disclosed in Japanese Patent Application No. 60-64803. This lifting apparatus has a single stretchable boom mounted on a vehicle for lifting a platform. This lifting apparatus has a simple constitution and facilitates the inspection and manufacture thereof. However, in this lifting apparatus, dexterous operation is required for stably moving the platform in a horizontal direction at an elevated level and it is very difficult to lift the platform repeatedly to a fixed elevated position.
Accordingly, it is an object of the present invention to provide a lifting apparatus having a single stretchable boom and simple constitution, facilitating manufature and inspection, and capable of smoothly raising or lowering the platform through the electronic control of the platform lifting operation.
It is another object of the present invention to provide a lifting apparatus capable of smoothly and vertically moving the platform.
It is a further object of the present invention to provide a lifting apparatus capable of smoothly and horizontally moving the platform at an elevated level.
It is a still further object of the present invention to provide a lifting apparatus capable of storing the data of a desired elevated position in a memory and automatically and repeatedly moving the platform between a reference level and the desired elevated position corresponding to the data stored in the memory.
According to one aspect of the present invention, there is provided a lifting apparatus comprising: a mobile vehicle; stretchable boom consisting of a plurality of booms inserted one in another in telescopic fashion and pivotally supported on the mobile vehicle; a platform pivotally joined to the free end of the stretchable boom; extension detecting means for detecting the working length of the stretchable boom; inclination detecting means for detecting the inclination of the stretchable boom with respect to a reference plane; and hydraulic control system for controlling the strechable boom on the basis of signals given thereto by the extension detecting means and the inclination detecting means wherein the stretchable boom is controlled so that the platform is raised vertically.
According to another aspect of the present invention, there is provided a lifting apparatus comprising: a mobile vehicle; a stretchable boom consisting of a plurality of booms inserted one in another in telescopic fashion and pivotally joined to the free end of the stretchable boom; extension detecting means for detecting the working length of the stretchable boom; inclination detecting means for detecting the inclination of the stretchable boom with respect to a reference plane; and a hydraulic control system for controlling the stretchable boom on the basis of signals give thereto by the extension detecting means and the inclination detecting means so that the platform is raised vertically and is moved horizontally at an elevated level.
According to a further aspect of the present invention, there is provided a lifting apparatus comprising: a mobile vehicle; a stretchable boom consisting of a plurality of booms inserted one in another in telescopic fashion and pivotally supported on the mobile vehicle; a platform pivotally joined to the free end of the stretchable boom; extension detecting means for detecting the working length of the stretchable boom; inclination detecting means for detecting the inclination of the stretchable boom with respect to a reference plane; an electronic control system; and a hydraulic control system for controlling the stretchable boom on the basis of signals given thereto by the extension detecting means and the inclination detecting means and also on the basis of data regarding a position of the platform stored in the memory of the electronic control system, wherein the platform can be raised vertically through manual or automatic operation, the platform can be moved horizontally at an elevated level through manual or automatic operation, and the platform can be moved repeatedly and automatically between a reference position and a desired elevated position stored in the momory of the electronic control system.
The lifting apparatus according to the present invention is constituted on the basis of the following principle, which will be described hereinafter with reference to FIGS. 11 and 12.
Referring to FIG. 11, a stretchable boom T consists of a first boom P, a second boom Q, a third boom R and a cover members S which are connected telescopically so as to be slidable relative to the adjacent booms. The first boom P is joined pivotally at the lower end thereof with a pin O to a pair of brackets N fixed to the upper surface of a vehicle M serving as the base. A platform V is joined pivotally with a pin W to the upper end of the cover member S. When the stretchable boom T is extended to a length Ln (n=an optional integer), the inclination .theta.n of the stretchable boom T is regulated so as to meet EQU Ln.multidot.cos .theta.n=(C=a constant) (1)
For example, when L1.multidot.cos .theta.1=L2.sqroot.cos .theta.2=L3.multidot.cos .theta.3=C, the horizontal distance between the center of the pin O and the center of the pin W is always C, while the vertical distances between a reference plane including the center of the pin O and the center of the pin W are H1, H2 and H3, respectively. Accordingly, the platform V is raised vertically.
Principle for horizontally moving the platform V on a fixed elevated level will be described with reference to FIG. 12. According to this principle, the distance Lm between the center of the pin O and the center of the pin W, and the inclination .theta.m (m=an optinal integer) of the stretchable boom T are regulated so that EQU Lm.multidot.sin .theta.m=H (H=a constant) (2)
For example, when L1.multidot.sin .theta.1=L2.multidot.sin .theta.2=H, the vertical distance between the center of the pin W and the reference plane is always H, while the horizontal distances between the center of the pin O and the center of the pin W are C1 and C2, respectively. Accordingly, the platform V is moved horizontally on a fixed elevated level at a height H.
The above and other objects, features and advantages of the present invention will become more apparent from the following description accompanying drawings.